Creatures... Devil.... Demon....
They're all beasts in various guises. If things went wrong in an Empire where Demons are sought by creatures, a war may erupt.
Due to complications in birth, a little girl from the Imperial Family was born and became a demon vessel. The Emperor realized it would be dangerous for her to be discovered, so they hid her inside the palace walls and provided her everything she desired in order for her to enjoy a happy life even though she was isolated from the outside.
Except for a few close family and acquaintances, no one knew she existed. Empire citizen assumed she perished shortly after birth.
She is Nashtassia Freya Marqueza, the youngest daughter of the Emperor and Empress Marqueza, as well as the new vessel of the demon, Raum, the son of the Demon Lord.